Three dimensional sculptures are best, but if you really want to paint a medallion, I guess that's alright.

You can paint your horse with oils

acrylics...

pastels or any other medium that strikes your fancy.

Basically, the only rule that really matters is that you start February 1 with an unpainted model...

prepped and primed is fine...

and finish February 28 with a fully painted horse!

There may be some other optional parts to this challenge that include official registration, critiques and swag. I'm still working on that. Mostly, however, this is a fun challenge designed to get people painting. Feel free to adapt it to suit your own means. I promise, I won't be offended!

I have that problem too - 18 million reference pictures (or so) in my library, and counting... While the number of horses I actually paint has been in the single digits each year (if that). Hoping to change that this year, and this will be a good push. :)